Development and Control of Xy Stage with a Hybrid Bolt Clamped Langevin Type Ultrasonic Motor

The development and control of XY stage driven by ultrasonic linear motor is presented. In this paper, the stage is driven by the hybrid-bolt clamped Langevin-type (Hybrid BLT) ultrasonic motor which consists of a longitudinal and a lateral PZT. The hybrid BLT is excited by its matched natural frequency without a discordance between natural frequency of a 3rd longitudinal mode and a 6th lateral mode. For fine and stable control performance, Nominal characteristics trajectory following (NCTF) control method is adopted. The NCTF control method does not require an exact mathematical model of the Hybrid BLT and is determined with open loop response based on simple experiment. Consequently, the experimental result shows that the BLT system achieved nanometric accuracy. INTRODUCTION The ultrasonic linear motor have many advantages compared to conventional electromagnetic motors, such as high power, nanometric accuracy in the long stroke, simple mechanism. [1]. This paper presents development and control of XY stage with Hybrid BLT ultrasonic motor to achieve stable, high power, long stroke and nanometer accuracy [2]. SYSTEM CONFIGURATION The configuration of Hybrid BLT system is expressed as figure. The Hybrid BLT is 20mm in diameter and 247mm in length in shape of long bar. It has two types of PZT elements to excite two modes (longitudinal and lateral mode). The Alumina was used to provide the driving force, attached to a maximum vibration point on the BLT. Moreover, contacting surface is also made of alumina and it is attached to the slider. The support was placed at the node point, composed of disk spring and bolt. The disk spring was thrust into actuator and preload was applied by a spring. FIGURE 1. Schematics of the XY Stages TABLE 1. Specifications of the XY Stages